1. Field of the Invention
The present invention relates to an information storage medium on which information is written by being irradiated with a laser beam. More particularly, the present invention relates to an information storage medium with three or more information storage layers and an information writing device that is compatible with such an information storage medium.
2. Description of the Related Art
Various types of information storage media, on which information can be written by being irradiating with light that has been modulated so as to represent the information to write (such as a laser beam), have been developed extensively as means for storing a huge amount of information thereon. Examples of those information storage media include a write-once information storage medium, on which information can be written only once on each particular area, and a rewritable information storage medium, on which information can be rewritten an unlimited number of times. Those two types are generally called a “write-once optical disc” and a “rewritable optical disc”, respectively.
To increase the storage capacity of an optical disc by leaps and bounds, it is an effective measure to take to get multiple storage layers stacked one upon the other in a single optical disc. As for DVDs and BDs, dual-layer discs with two information storage layers are already available.
Such an optical disc has a test write zone for determining appropriate writing conditions for writing information (such as the recording power of the light, among other things) in each of its information storage layers. In writing information on an optical disc using an optical disc drive, the recording power is optimized using the test write zone when the drive is being loaded with the disc or just before data is actually written on it. For example, Japanese Patent Application Laid-Open Publication No. 2002-358648 discloses a method for determining the recording power for a write-once optical disc.
Japanese Patent Application Laid-Open Publication No. 2002-358648 does disclose techniques applicable to an optical disc with two information storage layers but discloses nothing about the structure of an optical disc with three or more information storage layers (e.g., the arrangement of test write zones and how to use them, among other things).